This invention pertains to bellows forming generally as disclosed in U.S. Pat. No. 3,429,160, whereby a series of circumferential convolutions are formed in the elongated tubular wall of a flexible metal blank. Such bellows have many uses, typically in expansion joints for power plants, nuclear reactors, and other systems.
In known methods to form such bellows, interior and exterior forming rolls are brought together against opposite sides of the wall of the blank, as the blank is rotated about its axis, to form each convolution in the wall of the blank. As in U.S. Pat. No. 3,429,160, the exterior forming rolls are carried by two bell crank arms actuated by hydraulic means, which may not provide sufficient rigidity, as the interior forming roll is forced against the wall of the blank, to provide accurate dimensional control of each convolution.
In such methods, the blank must be indexed manually, by approximate reference to each previously formed convolution, for each convolution to be successively formed. Hence, any dimensional errors from one convolution to the next tend to be cumulated.